JPH04228598A - Method for adjusting thickness of photoresist film and stability of electrodeposition vessel - Google Patents

Abstract

PURPOSE: To coat a uniform photosensitive film at a desired thickness and to stabilize an electrodeposition vessel by adding a flux to a photoresist compd.

CONSTITUTION: The thickness of the electrodeposited photoresist is adjusted by adding the flux forming the uniform film of a desired thickness by eutectoid of the photoresist to the photoresist compd. Ethylene glycol ethylhexyl ether, etc., are used as the flux. A conductive surface is coated with this photoresist by electrophoresis, etc. The amt. of the flux to be added is preferably about 25 wt.% of an emulsion. The added flux improves the quality of the film and acts to adjust the thickness of the adhered film. The coating film may be obtd. at a lower temp. than heretofore.

COPYRIGHT: (C)1992,JPO

Description

[Detailed description of the invention]

[Background of the invention] 1. INTRODUCTION This invention relates to photosensitive polymer compositions and their use in electrodeposition processes for applying adherent, uniform photosensitive films onto conductive surfaces at desired thicknesses. .

More specifically, the present invention relates to the use of charged carrier groups.
a photoinitiator, and a source of unsaturation for crosslinking an electrodeposited film upon exposure to actinic radiation; This includes adding a coalescing agent to the polymeric composition that lowers the working temperature of the composition and increases its stability over time and temperature.

The improved polymer compositions of the present invention can be electrodeposited onto conductive surfaces at desired thicknesses as homogeneous, aqueous, developable films that are resistant to strong inorganic acids and aqueous. It is also resistant to bases.

2. DESCRIPTION OF THE PRIOR ART Photoresists are, for example, printed circuit boards or lithographs.
A photosensitive film that can transfer an image onto a conductive surface, such as a metal surface. Liquid photoresists typically include a film made of a resin or polymer and a photosensitive compound or photoinitiator dissolved or suspended in a solvent such as an organic liquid.

[0005] Liquid photoresists are used in negative-acting systems.
m) is also a positive system (positive-ac)
ting system) is also possible. Photoresist as negative or negative resist
After the film is electrodeposited on a surface, the solvent is removed, such as by heating, and the film is selectively exposed to an energy source, such as ultraviolet light, usually through a photomask. A photomask has a portion that is opaque to radiation and a portion that is transparent. The pattern of the photomask created by its opaque and transparent parts defines the desired image, for example a circuit, which is transferred to the surface of the support. The exposed portions of the negative resist film become less soluble in the phenomenon liquid than the unexposed portions due to the photochemical reaction between the photoinitiator and the polymer or resin that occurs during exposure. This difference in solubility selectively removes the unexposed film and transfers the image to the surface.

[0006] Positive resist
sist), the exposed parts of the film become more soluble in the phenomenon liquid than the unexposed parts as a result of a photochemical reaction, thereby selectively removing the exposed parts. After development of either type of resist film, the portions of the surface not protected by the resist can be etched, such as by the action of an oxidizing solution, usually containing an inorganic acid. The remaining resist film is then stripped from the surface leaving only the desired etched image on the support. Alternatively, the support surface containing the imaged resist can be plated with a metal or a combination of metals, such as tin and lead. The resist can then be selectively stripped away and the exposed metal on the support etched to create the desired pattern or circuit on the support surface. The historical background of conventional photoresists, types and operations date back to 1975.
Published in 2013 by McGarrow-Hill, W. S. DeForest
photoresist materials and processes (Photoresis
tMaterials and Processes
ses).

Liquid resists have been used for many years in lithography and electronic applications, and despite numerous improvements in resist systems and processing steps related to these applications. Conventional liquid resists still suffer from one or more problems. For example, it may be necessary to firmly adhere a liquid resist film to a surface to create a special surface. This increases processing time and costs. Also, the resist itself may require other specialized processing steps, such as curing or baking steps, which also increases processing times. Along with the loss of raw materials during film deposition, the cost of resist components used in conventional systems and the difficulty of creating stable systems with good reproducibility are also problems.

Liquid resist drawback
) is very widely known, but it makes it difficult to deposit films of uniform and appropriate thickness without creating pores or pinholes on the surface. Additionally, the resist must be resistant to etching and electroplating baths that operate over a wide range of applied radiation with minimal exposure doses and exposure times.

As mentioned above, the compositions of the present invention are particularly suitable for electrodeposition. Electrodeposition takes place in an electrolytic layer whose conductive surface coated with mobile charged particles serves as an electrode. Polymers that are positively charged in a medium are known as cationic polymers. The electrodeposition of a cationic polymer on the surface of a negatively charged electrode (cathode) is called cathodophoresis, while the electrodeposition of a negatively charged polymer (anionic polymer) on the surface of a positively charged electrode (anode)
Electrodeposition of is known as anodephoresis.

Coating organic materials and metal objects by electrodeposition is well known and is widely used for coating metal surfaces such as automobiles. Electrodeposition is also used to manufacture electrical components such as resistors and capacitors, which are essential to printed circuit boards (U.S. Pat. No. 3,303,
078).

Electrodeposition of photosensitive coatings is also well known. US Patent No. No. 3,738,835 contains polychloroprene polymer, 4,4'-bis-(dimethylamino) in 80% butyl acetate, 20% methyl ethyl ketone, or 80% cyclohexanone, 20% methyl ethyl ketone solvent.
Photosensitizers such as benzophenone
izer), stabilizers such as hydroquinone to prevent decomposition of unsaturated polymers in solution, and curing agents such as partially cured resins or other polymers to impart corrosion resistance. It is described that a photosensitive composition was deposited with a prepared emulsion. This emulsion is made by adding a fluorocarbon surfactant, N-methyl-2-pyrrolidone, and triethylamine to the previous solution. The photosensitive composition is exposed to radiation to crosslink the unsaturated polymer, and the unexposed film is developed with an organic solvent.

[0012] Japanese Patent Application No. No. 77-11601 describes a method for electrodepositing photosensitive polymer compositions onto silicate-coated metal surfaces. The photosensitive polymer can be dissolved or dispersed in an aqueous medium,
Furthermore, since it contains neutralized acidic groups, it is anaphoretically oriented toward conductive surfaces.
y) Electrodeposition is possible. The polymer is photosensitive because it contains unsaturated groups that crosslink when exposed to light.

[0013] Japanese Patent Publication No. 1 titled "Method for Manufacturing Printed Wiring Board" 55 (1989)-14891, the use of electrodeposition to coat a photosensitive material onto the copper surface of a copper laminate was reported in the manufacture of printed circuit boards. However, this reference does not describe any materials useful in the process or any process conditions used therein.

[0014] US Patent No. 4,592,816,
Photosensitive polymer compositions are described that can be electrodeposited as uniform photosensitive films onto electrically conductive surfaces. The thickness of the electrodeposited film can be adjusted by both the temperature and the electrodeposition potential used. In order to apply a thin coating, it is necessary to operate at a higher temperature and a lower potential. The higher the potential, the thicker the coating. Both of these methods used to adjust the thickness have a detrimental effect on the electrodeposition bath and the quality of the electrodeposited film. The components of the bath are unstable at high temperatures for long periods of time, and when the temperature is raised higher, they become hard and brittle with reduced sensitivity.
Usually a cracked coating will be obtained. Higher potentials will generate bubbles that will adhere to the surface and cause pinhole defects, thus having a negative effect on the electrocoated film quality.

US Pat. No. 4,810,738 describes additive compositions for making thicker films using electrodeposition techniques. The composition is a multicomponent system, including a surfactant, a viscosity modifier, and another immiscible solvent. In order to obtain the desired thickness, they must be mixed in precise relative amounts. This additive composition is not used to lower the operating temperature of the bath, nor is it intended to produce pinhole-free coatings at electrodeposited thicknesses.

[Summary of the Invention] A photosensitive compounding tank (
formation baths) were unstable where high temperature operations were required to deposit the thin coatings necessary for printing and use as etch resists. The life of the bath was less than a week, and the coatings obtained using these conventional chemical techniques were full of pinholes.

[0017] By adding certain ingredients to the bath, a film with a desired thickness or thinness can be obtained at a lower working temperature, and the additives also contribute to the stability of the bath. It was found that The film thus obtained is uniform and free of pinholes.

Furthermore, it has been found that both water-soluble or partially water-soluble agents as well as water-insoluble agents lower the operating temperature and substantially increase the bath stability of the electrodepositable photosensitive composition. Served.

These additives, because of their low volatility and partition coefficient, essentially remain in the emulsion and are removed by deposition with the photoresist. In this case, the additives have the function of improving the quality of the film and adjusting the thickness of the deposited film. By selecting the additives and their quantities in the bath, it is possible to adjust the thickness of the deposited film and the temperature that allows the desired thickness. The fusing and leveling properties of the coated film are significantly increased by storage or even by standing. In this way, small defects that would otherwise be present are effectively eliminated.

In contrast to the improved films made by the method of the present invention, thick coatings obtained using prior art electrodeposited photoresist systems have significantly more pinholes. Using the additives of the present invention in electrodeposited photoresist systems, film thicknesses can be up to twice the normal thickness at lower operating temperatures. This type of coating has no pinholes and has no plating resist.
Suitable for use as t).

[Description of Preferred Specific Examples] Electrodepositable coating compositions that can be used in the present invention include US Patent No.
．． 4,592,816 and U.S. Pat. 4,632,
900 are suitable, and these patents are incorporated herein by reference. These compositions include one or more polymers containing a carrier group and, if the composition is used as a photoresist, optionally a photoinitiator and a source of unsaturation for the crosslinking reaction. Sometimes. Monomers are preferred for this source of unsaturation.

The polymeric component of the composition contains carrier groups that are either positively or negatively charged with acids or bases, depending on the particular carrier group used. The carrier group is chosen such that the electrodeposited film is expected to be developable in acidic or basic aqueous solutions. Suitable polymers are addition polymers and condensation polymers having carrier groups as described above. Addition polymers with carrier groups formed from monomers with ethylenically unsaturated properties are desirable. Carrier group-containing polymers useful in photopolymer compositions include acrylic polymers, vinyl polymers other than acrylic polymers, epoxy polymers, polyurethanes, polyesters, and polyamides.

A polymer having a positively charged carrier group, ie, a cathodophoretic carrier group, is deposited on the negatively charged electrode. For example, such carrier groups include quaternary ammonium groups and phosphonium groups that react with acids to become positively charged. Acids useful for protonating the carrier groups of polymers include lactic acid, formic acid, acetic acid, and phosphoric acid.

[0024] A polymer having negatively charged carrier groups, ie, anti-anodophoretic carrier groups, is deposited on the positively charged electrode. Carboxylic acids are suitable as negatively charged carrier groups.

For photoactivated coatings, the polymer having a carrier group is combined with one or more unsaturated monomers and a polymer such that the polymer film electrodeposited on the surface can be polymerized into a crosslinked polymer when exposed to actinic radiation. Mixed with a photoinitiator to produce preferred compositions suitable for electrodeposition. The unsaturated monomer preferably has two or more unsaturated groups attached to the same molecule. Examples of suitable monomers are reported in the referenced patents mentioned above. Photoinitiators suitable for use in the polymer compositions include azo compounds, sulfur-containing compounds, metal salts, metal complexes, oxines, amines, polynuclear compounds, organic carbonyl compounds, various quinones, and the like. Specific examples of suitable photoinitiators are described in U.S. Pat. It is also reported in No. 4,592,816.

For purposes of the present invention, preferred electrodepositable compositions, expressed in terms of relative concentrations of polymer, photoinitiator, unsaturated monomer and acid, are shown in the following table (100 parts by weight of polymer and weight):

[0027]

[Table 1]

As will be apparent to those skilled in the art, the composition may include colorants, plasticizers, wetting agents and other additives such as those commonly used in electrodeposition baths. These additive components have been used to enhance the adhesion of the substrate; they do not adjust the thickness of the deposit.

A coalescing agent is added to the photopolymer composition to enable more uniform application of the photoresist to the support at the desired thickness. Having the coalescing agent partitioned into and deposited with the photoresist micelles facilitates film formation through deposition and subsequent baking. The coalescing agent also softens the micelles, resulting in a thin but not hard coating, unlike prior art coatings.

Preferred coalescents include those that are water-soluble or partially water-soluble, and those that are water-insoluble. Among the water-soluble or partially water-soluble coalescing agents, 1-nitropropane, 2-nitropropane,
- Nitropropane, M-pyrrole (methyl-pyrrolidone), ethylene glycol ethylhexyl ether, propylene glycol methyl ether, high molecular weight polypropylene glycol and Texanol (2,2,4-trimethyl 1,3-pentanediol monomer from Eastman Kodak) isobutyrate) is preferred. Other fusion agents include Modaflow (Monsanto
copolymers of ethyl acrylate, such as oleyl alcohol,
xrecin) (Caschem's resinoleic acid polyol), FC430 (3M's fluorocarbon surfactant) and Foamkill 639AA (F
orm kill 639AA) (defoaming agent). Lubricant agents useful as coalescing agents include oleamide and Lubrizo 5907.
There are high molecular weight polymers such as 15907). EM-1
Waxes such as 1 and EM-937 (available from Axel Manufacturing) can also be used. The most preferred coalescing agent is ethylene glycol ethylhexyl ether.

The distribution coefficient of the coalescing agent determines how much is deposited with the film. The amount of coalescing agent used can vary depending on a number of factors, including the partition coefficient of the selected coalescing agent between the organic micelles and the aqueous phase. Coalescing agents are usually added to the bath before emulsification (ie, before adding water in Table I above). Regarding such factors, see T. N. Selecting Solvents for Visser's Electrodeposition Paints
for Electrodeposit Paint
s,, 18th edition (volume 1-B) pages 367-394 (1
It is well described in 986).

In general, for water-soluble or partially water-soluble coalescents, the amount can be up to about 25 wt% of the emulsion (including solid and aqueous parts), and about 10-20 wt%.
% and most preferably about 14-18 wt%. For water-insoluble coalescents, the amount can be up to about 15 wt% of the solids used to make the emulsion, and about 2 to 10 wt%.
wt% is preferred, and about 4-6 wt% is most preferred.

The present invention will be further explained with reference to the following examples which will be helpful in understanding the invention but are not meant to be limiting thereof.

[0034]

[Example] [Example 1] Electrodeposition composition polymer 91.0 g Dimethylaminoethyl methacrylate 8 parts Methyl methacrylate 75 parts Ethyl acrylate 1
7 parts Monomer 46.0 g Dipentaerythritol monohydroxy penta-acrylate paint 1.1 g Morton Thiokol
) Molton ERO Blue fusion agent 160.0g Propylene glycol methyl ether photoinitiator 11.0g 2-methyl-1-[4-(methylthio)phenyl]-2
-morpholino-propan-1-one
8.3g isopropylthioxanthone 2.7g acid
15.0g lactic acid 20% Add distilled water until it reaches 1000g Temperature of tank: 20℃ Voltage: 50V Time:
10 seconds Typically, a portion of the above composition is placed in a 250 ml beaker used as a plating cell. A 1" x 2" stainless steel plate was used as the anode and the basic material of the circuit board was used as the cathode. The distance between the anode and cathode was 2 inches. Coating was carried out under the conditions listed in the table above. Furthermore, in order to determine the thickness of the applied coating film, the thickness was measured. The measurement was carried out using “Microd” manufactured by UPA Technology.
erm), or a
The Sloan Technology Co., Ltd.
Technology Company)
This can be done using methods well known in the art, including the use of a profilometer such as the Dektak. The thickness of the coating obtained under the above conditions is 5 microns. Met.

Example 2 The following table shows a comparison of thickness versus temperature distribution for the photoresist formulation of Example 1 in which the preferred coalescing agent is ethylene glycol ethylhexyl ether (EEH). The conditions for attaching the resist are as in Example 1.
I made it the same as The data shown are measurements of the thickness of the applied plating with and without the addition of EEH to the bath composition:

[0036]

[Table 2]

The above table shows that desirable thin coatings (typically <10 microns) for use as printing and etch resists were obtained at temperatures 15 degrees lower than when no coalescing agent was added. There is. Also, at higher temperatures above that temperature scale, deposition of thinner coatings was expected, whereas thicker coatings suitable for use as plating resists (typically >10
micron) was obtained by addition of a coalescing agent. These thicker coatings did not exhibit the pinholes seen in prior art coatings of comparable thickness or coatings deposited at lower temperatures.

Example 3 The amount of coalescing agent in the bath also determines the thickness of the coating at various temperatures. This was evidenced by the following table showing the temperature vs. thickness distribution when varying the amount of propylene glycol methyl ether added to the photoresist formulation obtained in Example 1:

[0039]

[Table 3]

By selecting the appropriate temperature and the appropriate amount of coalescing agent, the thickness of the coating can be adjusted to produce thin or thick coatings at temperatures lower than those required for conventional bath compositions. It is now possible to obtain membranes.

[Example 4] Electrodeposition composition dimethylaminomethyl methacrylate
Ethyl methacrylate-methyl methacrylate copolymer 43.7g Dipentaerythritol monohydroxypenta-acrylate 13.
2g 2-isopropylthioxanthone

0.6g 2-methyl-1[4-(methylthio)phenyl]-2-morpholino-propan-1-one
2.1g 9-10 anthracenedione, 1,4-bis(alkylamino) 0.3g
20% lactic acid aqueous solution

2.6g The tank was divided into two parts and 8g of the coalescing agents 1-nitropropane and 2-nitropropane were added to each part. At room temperature (25℃), 5
A voltage of 0 volts was applied for 10 seconds. The thickness of the coating electrodeposited in both baths at 100 millijoule photospeed was 5 microns, indicating that the photospeed was not adversely affected.

The present invention has been described in detail, including preferred embodiments thereof. However, it is possible for a person skilled in the art to make changes and/or improvements to the present invention upon consideration of the present invention, and such changes and modifications may be made within the scope and spirit of the present invention as set forth in the claims. It's obvious.

Claims (18)

[Claims] 1. A coalescing agent (coa) is added to the photoresist formulation to codeposit the photoresist and form a uniform film of desired thickness.
1. A method of adjusting the thickness of an electrodeposited photoresist, the method comprising adding a less recent agent. 2. The method of claim 1, wherein the photoresist formulation includes a solvent, a polymer, an unsaturated monomer, a photoinitiator, an electrolyte, and water. 3. The fusing agent is 1-nitropropane,
2-nitropropane, methylpyrrolidone, ethylene glycol, ethylhexyl ether, propylene glycol methyl ether, 2,2,4-trimethyl-1,3-
A claim selected from the group consisting of pentanediol monoisobutyrate, high molecular weight polypropylene glycol, copolymers of ethyl acrylate, oleyl alcohol, resinoleic acid polyols, high molecular weight fluorocarbon surfactants, defoamers, oleamides and waxes. Item 1
the method of. 4. The method of claim 1, wherein said coalescing agent is ethylene glycol ethylhexyl ether. 5. The photoresist is subjected to electrophoresis (ca
2. The method of claim 1, wherein the coating is applied taporetically. 6. The photoresist is subjected to electrophoresis (an
2. The method of claim 1, wherein the coating is coated aphoretically. 7. The amount of the fusing agent added is 25w of the emulsion.
2. The method of claim 1, wherein the amount is t% or less. 8. The method of claim 1, wherein the coalescing agent is selected based on a 50/50 organic/aqueous partition coefficient. 9. The method of claim 1, wherein said uniform film of desired thickness is within the range of 1 to 50 microns. 10. A method for adjusting the working temperature of an electrodeposition photoresist bath, which comprises adding a coalescing agent to the electrodeposition photoresist bath in order to lower the working temperature of the bath. 11. The method of claim 10, wherein said working temperature is within the range of 5 to 40°C. 12. The method of claim 10, wherein the photoresist formulation includes a polymer, a solvent, an unsaturated monomer, a photoinitiator, an electrolyte, and water. 13. The coalescing agent is 1-nitropropane, 2-nitropropane, methylpyrrolidone, ethylene glycol ethylhexyl ether, propylene glycol methyl ether, 2,2,4-trimethyl-1,3-
Claim 10 selected from the group consisting of pentanediol monoisobutyrate, high molecular weight polypropylene glycol, copolymers of ethyl acrylate, oleyl alcohol, resinoic acid polyols, high molecular weight fluorocarbon surfactants, defoamers, oleamides and waxes. the method of. 14. The method of claim 10, wherein said coalescing agent is ethylene glycol ethylhexyl ether. 15. The method of claim 10, wherein the photoresist is applied cathodophoretically. 16. The method of claim 10, wherein said photoresist is applied anodic electrophoretically. 17. The amount of the fusing agent added is 25% of the emulsion.
11. The method of claim 10, wherein the amount is less than or equal to wt%. 18. The coalescing agent is selected on the basis of an organic/aqueous partition coefficient of 50/50.
0 method.